The pledging back-of-the-envelope calculation got me curious, because I had been assuming GWWC wouldn't flat out lie about how much had been pledged (they say "We currently have 291 members ... who together have pledged more than 112 million dollars" which implies an actual total not an estimate).

On the other hand, it's just measuring pledges, it's not an estimate of how much money anyone expects to actually materialise. It hadn't occurred to me that anyone would read it that way - I may be mistaken here though, in which case there's a genuine issue with how the number is being presented.

Anyway, I still wasn't sure the pledge number made sense so I did my own back-of-the-envelope:

£72.68M pledged 291 members £250K pledged per person over the course of their life 40 years average expected time until retirement (this may be optimistic. I get the impression most members are young though) £6.2K average pledged per member per year

That would mean people are expecting to make £62K per year averaged over their entire remaining career, which still seems very optimistic. But:

• some people will be pledging more than 10%
• there might be some very high income people mixed in there, dragging the mean up.

So I think this passes the laugh test for me, as a measure of how much people might conceivably have pledged, not how much they'll actually deliver.